DEJA BOO: The night after a police officer chased down and uses his Taser gun on a Phillies fan, another one (above) ran onto the field last night in front of the Phillies' Jayson Werth. Photo: AP

We’ve been heading toward this for more than 40 years, if you think about it. It was the ’69 Mets who perfected the notion that spectator sports could be participation sports; three times that October, the Mets clinched various levels of baseball primacy at Shea Stadium, and three times — division title, pennant, World Series — the fans turned the turf at old Shea into impromptu Woodstock gatherings.

In the beginning, it all seemed so innocent: instant celebrations, the culmination of a summer of baseball love. This wasn’t invented in New York — pictures of the swarming of the field at Fenway Park when the Red Sox clinched the pennant on the last day of the ’67 pennant are still prominent features of any Boston watering hole worth its Sam Adams kegs.

As time went on, though, the whole notion of fans crossing the threshold morphed from being cute and innocent to something darker. Idiots threw whiskey bottles at Pete Rose during the 1973 NLCS. Three years later, Chris Chambliss had to make like Earl Campbell to survive his pennant-winning tour of the Yankee Stadium basepaths. The day baseball returned to New York after the ’94-’95 strike, fans ran on the field to throw faux money at ballplayers.

Gunther Parche, an unemployed German lathe operator, crossed the last uncrossable line 17 years ago last week, when he stabbed Monica Seles during a tennis tournament in Hamburg. And it was nine years after that when William Ligue Jr. and his 15-year-old son jumped out of the stands at Comiskey Park to attack a Royals coach named Tom Gamboa.

So, no, that fan in Philadelphia who got himself good and tased Monday night, 17-year-old Steve Consalvi, didn’t just take one for himself. He took one for the team of imbeciles who’ve been leaping onto fields for 40 years and making themselves into look-at-me nuisances, making the athletes feel less and less like they’re working in athletic sanctuaries and more and more like they’re targets in a shooting gallery.

“Look, no one wants to ever come out and say this, but a lot of guys get freaked out when they see a guy jump over the fence and hold up a game,” an ex-major leaguer who spent a fair chunk of his career in New York told me yesterday, though he didn’t want his name used because the feelings he voices don’t exactly match the tough-guy image most big leaguers like to project.

“I realize that 99.9 percent of the dumb-asses who do this are drunk out of their minds and won’t do any harm to anyone, they’re doing it for [kicks] and giggles or on a dare from their buddies. But you know something? One of these days, that .01 percent guy is going to wander up to someone with a pocketknife hidden in his socks, and when that happens, it’s never going to be the same ever again. For anyone.”

The civil libertarians can have their field day talking about the cruel sight of a fan going down at the hand of a Taser, but they might want to talk to Seles first. A few years ago, at the Open, after one of the early-round departures that marked the latter years of her career, Seles admitted, “I don’t know that I’ll ever feel as comfortable on a tennis court as I did before.”

She didn’t have to explain “before.” And for now, the rest of sport really still resides in “before.” Ligue and son nearly dragged us to “after,” the ugliness at Auburn Hills nudged us ever closer. If you don’t think there’s enough anger out there to someday push a fan to tackle a manager on the way to making a pitching change, you don’t read enough message boards, listen to enough talk radio.

You say tasing a fan crosses a line? Fine. You’re entitled.

But another knucklehead took to the field in Philadelphia last night. The cops didn’t tase him, but after Cole Hamels promptly coughed up a ninth-inning lead, it’s possible Phillies fans had something else in store for him. And I’m fine with that, too.